Field of Invention
The invention generally is related to the area of antennas, and more particularly related to integrated antenna arrays structured in a way and controlled electronically to form a desired antenna pattern, wherein the desired antenna pattern can be controlled to demonstrate identical main beam radiation characteristics for independently polarized antennal elements.
Related Art
An antenna system is an indispensable component in communication systems. In conventional wireless communications, a single antenna is used at the source, and another single antenna is used at the destination. Physically, an antenna (or aerial) is an electrical device which converts electric power into radio frequency (RF) energy or waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an oscillating radio frequency electric current to the antenna, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage to be supplied to a receiver to be amplified.
Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, broadcast television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, Bluetooth enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise. Typically an antenna is an arrangement of metallic conductors and electrically connected (often through a transmission line) to a receiver or a transmitter. An oscillating current of electrons forced through the antenna by a transmitter creates an oscillating magnetic field around the antenna conductors, while the charge of the electrons also creates an oscillating electric field along the antenna conductors. These time-varying fields, when created in the proper proportions, radiate away from the antenna into space as a moving transverse electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna conductors, causing them to move back and forth, creating oscillating currents in the antenna.
It is well known that the RF energy radiated from an antenna system has its very unique polarization which depends on the geometry and the orientation of the antenna system. Typically, the polarization can be linear or elliptical. More specifically, linear polarization covers vertical polarization and horizontal polarization, and elliptical polarization covers circular polarization. Regardless, the very fundamental polarizations are vertical and horizontal polarizations. All other polarizations are simply the linear combinations of these two fundamental polarizations. For any transmission and reception of the RF energy, if the polarization of the transmitting antenna and the polarization of the receiving antenna do not line up, the RF energy would be lost, resulting in a weak RF link between two communicating devices.
In the Wi-Fi arena, the antenna systems at client ends are typically structurally simple and respond only to linearly polarized RF signals. Moreover, the orientations of the polarization at the client ends (e.g., a communicating device) are often unpredictable. It is therefore desirable for the Wi-Fi service providers to provide a system that is capable of offering both horizontally and vertically polarized RF links simultaneously for each individual channel in order to establish reliable respective RF links with the clients. Operationally, the clients can be best served when the main beam radiation characteristics of both the vertically polarized and the horizontally polarized RF energy are identical or substantially similar. Although it is not difficult to design an antenna system which provides both vertically polarized and horizontally polarized RF links, it is not trivial to provide both vertically polarized and horizontally polarized RF links that have the substantially similar main beam radiation characteristics.
One embodiment of the present invention is to provide designs of antennas that can provide both vertically polarized and horizontally polarized RF links that have substantially similar main beam radiation characteristics. With the compact designs, the antennas can be very well used for mobile devices for wireless communications.